perl命令：批量修改替换文件

需求如下：有nginx负载均衡配置文件，更新某几台服务器需要先注释掉前端机器，需要用脚本实现；
之前一直用sed进行替换，遇到一个高手用perl命令也可以实现，命令更简洁直观，可以实现同样的效果。

举例如下：
[root@localhost ~]# cat host.conf
upstream test_server {
server 192.168.169.36:80;
server 192.168.169.37:80;
server 192.168.169.38:80;
server 192.168.169.39:80;
server 192.168.169.50:80;
server 192.168.169.51:80;
server 192.168.169.52:80;
}

打印匹配的行
[root@localhost ~]# perl -ne 'print if /192.168.169.3/' host.conf
server 192.168.169.36:80;
server 192.168.169.37:80;
server 192.168.169.38:80;
server 192.168.169.39:80;
[root@localhost ~]# perl -ne 'print if /192.168.169.5/' host.conf
server 192.168.169.50:80;
server 192.168.169.51:80;
server 192.168.169.52:80;

perl命令：匹配192.168.169.3 网段的前面加#；
-i 写入到文件
[root@localhost ~]# perl -i -pe 's/(.*)/#$1/ if /192.168.169.3/' host.conf
执行结果如下：
[root@localhost ~]# cat host.conf
upstream test_server {
#server 192.168.169.36:80;
#server 192.168.169.37:80;
#server 192.168.169.38:80;
#server 192.168.169.39:80;
server 192.168.169.50:80;
server 192.168.169.51:80;
server 192.168.169.52:80;
}

同理，去掉#
[root@localhost ~]# perl -i -pe 's/#(.*)/$1/ if /192.168.169.3/' host.conf
[root@localhost ~]# cat host.conf
upstream test_server {
server 192.168.169.36:80;
server 192.168.169.37:80;
server 192.168.169.38:80;
server 192.168.169.39:80;
server 192.168.169.50:80;
server 192.168.169.51:80;
server 192.168.169.52:80;
}

匹配192.168.169. 网段的所有机器加#
[root@localhost ~]# perl -i -pe 's/(.*)/#$1/ if /192.168.169./' host.conf
[root@localhost ~]# cat host.conf
upstream test_server {
#server 192.168.169.36:80;
#server 192.168.169.37:80;
#server 192.168.169.38:80;
#server 192.168.169.39:80;
#server 192.168.169.50:80;
#server 192.168.169.51:80;
#server 192.168.169.52:80;
}

perl命令也支持类似sed的关键字替换
[root@localhost ~]# perl -pe 's/server/master/ if /192.168.169.3/' host.conf
upstream test_server {
master 192.168.169.36:80;
master 192.168.169.37:80;
master 192.168.169.38:80;
master 192.168.169.39:80;
server 192.168.169.50:80;
server 192.168.169.51:80;
server 192.168.169.52:80;
}

问题来了，实际配置文件基本都是同一个网段的ip，如果匹配的话，会匹配到其他机器上面，问题就严重了，所以需要按指定行进行精确匹配；
[root@localhost ~]# cat host.conf
upstream test_server {
server 192.168.169.36:80;
server 192.168.169.37:80;
server 192.168.169.38:80;
server 192.168.169.39:80;
server 192.168.169.50:80;
server 192.168.169.51:80;
server 192.168.169.52:80;
}

perl命令，匹配指定的行
if 判断 $. 行数，与或关系进行匹配；
[root@localhost ~]# perl -ne 'print if $.==2 ' host.conf
server 192.168.169.36:80;
[root@localhost ~]# perl -ne 'print if $.==4 ' host.conf
server 192.168.169.38:80;
[root@localhost ~]# perl -ne 'print if $.>=2 && $.<=5 ' host.conf
server 192.168.169.36:80;
server 192.168.169.37:80;
server 192.168.169.38:80;
server 192.168.169.39:80;

精确匹配，进行替换，大于等于第2行，小于等于第5行；
[root@localhost ~]# perl -pe 's/(.*)/#$1/ if $.>=2 && $.<=5' host.conf
upstream nav1_server {
#server 192.168.169.36:80;
#server 192.168.169.37:80;
#server 192.168.169.38:80;
#server 192.168.169.39:80;
server 192.168.169.50:80;
server 192.168.169.51:80;
server 192.168.169.52:80;
}

加-i 参数，将修改的操作写入到文件中；
[root@localhost ~]# perl -i -pe 's/(.*)/#$1/ if $.>=2 && $.<=5' host.conf